ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 263 



former, wMcli has not yet been detected in the latter ; and M, 

 Guignard has endeavoured to determine whether this diiference really 

 exists. The young embryo-sac of Lilium has a large nucleus situated 

 in the centre of a granular protoplasm which forms a sort of narrow- 

 meshed network filling up the cell. The long nuclear spindle is 

 remarkably clear, and at each of its extremities the chromatic threads 

 of which it is composed all converge to the same point. The 

 nuclear plate has the appearance of a star with twelve rays ; it is 

 formed of double often straight chromatic segments, with one ex- 

 tremity supported on a chromatic thread, the other turned towards the 

 periphery. At the two poles, suitable reagents, and especially bi- 

 chloride of mercury, reveal a radial disposition of the protoplasmic 

 granules. The radial arrangement of the protoplasm is also very 

 evident round the nuclei at the time when they are about to divide. 



The longitudinal doubling of the chromatic segments of the 

 nuclear plate above described is very evident in all nuclei the size of 

 which is sufficient to permit the observation ; as in the mother-cells 

 of the pollen of Liliaceee, Amaryllidefe, Eanunculaceas, Magno- 

 liacese, &c., in the endosperm after impregnation, and in other 

 vegetable tissues. In some other cases this doubling is difficult, or 

 almost impossible, to determine. 



Chromatine in Cell-division.* — A. Brass and Fraisse have in- 

 vestigated the part played by chromatine in the phenomenon of 

 cell-division. It is not constant, being wanting in cells that have 

 been starved for a time. It seems, therefore, to have no other function 

 than that of providing nutriment. Its staining properties are not a 

 proof of physiological importance. On the contrary, the active part 

 in these phenomena devolves upon the protoplasmic filaments which 

 do not take artificial colouring. Professor H. Folf has been able to 

 establish directly the movements of these" achromatic filaments during 

 the segmentation of the eggs of the sea-urchin. 



Siliceous Membrane with Properties of the Cell-wall.J — A. 

 Famintzin has constructed artificially, by the action of concentrated 

 hydrochloric acid on soda-glass, an excessively thin perfectly trans- 

 parent siliceous membrane having many of the properties of the cell- 

 wall and of starch-grains. These membranes allow osmotic currents 

 to pass freely through them, and their reactions with fuchsin and 

 carmine-solution are the same as those of vegetable membrane ; the 

 former they absorb eagerly with very deep staining, while towards 

 the latter they are perfectly indifferent. They also swell up in water 

 to the extent of about 5 per cent.; and this must therefore be re- 

 garded, not as a special property of organized structures, but rather 

 as one belonging to all colloidal bodies. 



* Arch. Sci. Pliys. et Nat,, xi. (1884) p. 320. 



t Loc. cit. 



X Bull. Acad. Imp. Sci. St. Petersbourg, xxix. (1884) pp. 414-6. 



